The present invention relates to a time division switching systems, and more specifically to a time division switching system which allows efficient utilization of time slots.
Advances in digital technologies have prompted the tendency toward the integration of voice and data switching services by a common time division switching system, and this tendency is particularly acute in digital private branch exchanges (PBX). A typical example of such PBX systems is shown and described in U.S. Pat. No. 4,253,179. In this switching system, a central controller accepts a service request originated by a line circuit and proceeds to write the address pair of originating and terminating line circuits into a sequentially addressable location of a control memory. An address counter is driven by a clock source to sequentially read and stored address pairs out of the memory into decoders for assigning a time slot to the line circuits of the address pair on a common bus of a switching network. This pathway is maintained until a clear request is deposited on the central controller. Although satisfactory for switching speech signals, the time slot utilization of the prior art switching system is not satisfactory for switching burst-type signals such as computer data. Another disadvantage is that the transmission capacity of the pathway is limited to a constant value, typically 64 Kbps, and as a result the system is not suitable for switching high-speed data.